Use HTTPS for releases

Makefile

@@ -21,7 +21,7 @@ archs := $(shell $(LUA) -e  \
 	< alpine-releases.conf.yaml)
 
 latest_releases_yaml = $(archs:%=latest-releases.%.yaml)
-releases_url := http://dl-master.alpinelinux.org/alpine/latest-stable/releases
+releases_url := https://dl-master.alpinelinux.org/alpine/latest-stable/releases
 releases_url_suffix = $(@:latest-releases.%.yaml=%/latest-releases.yaml)
 
 all: $(pages) $(static_out) $(out)/atom.xml $(out)/releases.json